Density, Viscosity, and Conductivity of [VAIM][TFSI] in Mixtures for Lithium-Ion Battery Electrolytes

Abstract

A novel unsaturated and amide-based ionic liquid, [VAIM]­[TFSI] (3-(2-amino-2-oxoethyl)-1-vinylimidazolium bis­(trifluoromethylsulfonyl)­amide), was synthesized using a two-step method. Its structure was confirmed by nuclear magnetic resonance, and its water content was determined by Karl Fischer titration to be below 0.03 wt %. The density, viscosity, and conductivity of the pure ionic liquid and its binary mixtures with acetonitrile were measured at various temperatures and at ambient pressure. Both the density and viscosity increase with the mole fraction of the ionic liquid and decrease with decreasing temperature. Excess molar volumes and viscosity deviations were calculated from the experimental results. The electrical conductivities in mixtures with different contents of the ionic liquid were investigated at different temperatures. The highest conductivity of binary mixtures is achieved at 0.07 mole fraction, with a value of ∼3.32 S·m–1 at 298.15 K. The conductivity of an electrolyte consisting of acetonitrile, LiTFSI, and the ionic liquid was measured to determine the optimal ionic liquid content. The suggested concentration is 3 wt% ionic liquid in this electrolyte, giving a conductivity of ∼4.11 S·m–1 at 298.15 K.